How to use the command 'stack' (with examples)
The ‘stack’ command is a tool for managing Haskell projects. It provides functionality to create new packages, compile packages, run tests, and more. This article will illustrate each of these use cases with examples.
Use case 1: Create a new package
Code:
stack new my-package
Motivation: Creating a new package is the first step when starting a new Haskell project. The ‘stack new’ command allows you to quickly generate the necessary files and directory structure for your project.
Explanation:
- ‘stack new’: This is the command to create a new package.
- ‘my-package’: This is the name you choose for your new package. Replace ‘my-package’ with your desired package name.
Example output:
Downloading template "new-template" to create project "my-package" in my-package/ ...
Use case 2: Compile a package
Code:
stack build
Motivation: Compiling a package is necessary to generate executable code from the Haskell source files. The ‘stack build’ command handles all the necessary dependencies and builds the package.
Explanation:
- ‘stack build’: This is the command to compile a package.
Example output:
Downloading rts-1.0 from hackage
...
Building library 'my-package'...
Use case 3: Run tests inside a package
Code:
stack test
Motivation: Running tests is crucial for ensuring the correctness of your code. The ‘stack test’ command executes all the tests defined within your Haskell package.
Explanation:
- ‘stack test’: This is the command to run tests inside a package.
Example output:
Running 1 test suite...
...
Cases: 7 Tried: 7 Errors: 0 Failures: 0
Use case 4: Compile a project and re-compile every time a file changes
Code:
stack build --file-watch
Motivation: During development, it can be tedious to manually recompile the project every time a file changes. The ‘–file-watch’ option enables automatic recompilation whenever a source file is modified.
Explanation:
- ‘stack build’: This is the command to compile a project.
- ‘–file-watch’: This option enables file watching for automatic recompilation.
Example output:
…
Building library 'my-package'...
File change detected. Starting incremental build...
Building library 'my-package'...
Use case 5: Compile a project and execute a command after compilation
Code:
stack build --exec "command"
Motivation: After compiling a project, sometimes it is necessary to perform further actions, such as running a specific command or script. The ‘–exec’ option allows you to specify a command to be executed after compilation.
Explanation:
- ‘stack build’: This is the command to compile a project.
- ‘–exec “command”’: This option specifies the command to be executed after compilation. Replace ‘command’ with the desired command.
Example output:
…
Building library 'my-package'...
Executing command: command
Use case 6: Run a program and pass an argument to it
Code:
stack exec program -- argument
Motivation: Sometimes, you need to run a specific program with certain arguments. The ‘stack exec’ command allows you to execute a program defined within your package and pass arguments to it.
Explanation:
- ‘stack exec’: This is the command to execute a program.
- ‘program’: This is the name of the program you want to run. Replace ‘program’ with the actual program name.
- ‘– argument’: This option allows you to pass arguments to the program. Replace ‘argument’ with the desired argument.
Example output:
Running program with argument: argument
Conclusion:
The ‘stack’ command is a versatile tool for managing Haskell projects. It provides convenient methods for creating packages, compiling code, running tests, and more. By following the examples provided in this article, you can effectively use the ‘stack’ command to streamline your Haskell development process.
